• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.7
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• pp.943-951
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• 1995

In this paper the projective controls, previously derived to preserve the dynamic modes of a state-feedback reference system, are extended to allow the preservation of the modes of a general output-feedback reference system. In general, the extension allows projective controls to be used as a controller approximation technique, where a reduced-order controller is designed to approximate the closed-loop behavior of the higher-order reference controller. This extension is useful if the best available reference control for the system is an output-feedback control. An example shows that the increased design freedom of proposed design method allows the stabilization of a given plant using a lower-order controller than the projective controls with state-feedback reference.

• Earthquakes and Structures
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• v.6 no.2
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• pp.217-235
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• 2014

In this paper, different feedback control strategies are presented for active seismic control using proportional-integral-derivative (PID) type controllers. The parameters of PID controller are found by using an numerical algorithm considering time delay, maximum allowed control force and time domain analyses of shear buildings under different earthquake excitations. The numerical algorithm scans combinations of different controller parameters such as proportional gain ($K_p$), integral time ($T_i$) and derivative time ($T_d$) in order to minimize a defined response of the structure. The controllers for displacement, velocity and acceleration feedback control strategies are tuned for structures with active control at the first story and all stories. The performance and robustness of different feedback controls on time and frequency responses of structures are evaluated. All feedback controls are generally robust for the changing properties of the structure, but acceleration feedback control is the best one for efficiency and stability of control system.

• Journal of applied mathematics & informatics
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• v.31 no.1_2
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• pp.247-262
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• 2013

In this paper, using the time scale calculus theory, we first discuss the permanence of a $n$-species competition system with feedback control on time scales. Based on the permanence result, by the Lyapunov functional method, we establish sufficient conditions for the existence and uniformly asymptotical stability of almost periodic solutions of the considered model. The results of this paper is completely new. An example is employed to show the feasibility of our main result.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.3
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• pp.134-141
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• 2003

PID controllers with constant gains have been widely used in various control systems due to its powerful performance and easy implementation. But it is difficult to have uniformly good control performance in all operating conditions. In this paper, we propose a nonlinear variable PR controller with immune feedback mechanism. An immune feedback mechanism is based on the functioning of biological T-cells, they include both an active term, which controls response speed. and an inhibitive term, which controls stabilization effect. Therefore, the proposed nonlinear PID controller is based on immune responses of biological. immune feedback mechanism which is the cell mediated immunity and In order to choose the optimal nonlinear PID controller games, we also propose the tuning algorithm of nonlinear function parameter in immune feedback mechanism. To verify performance of the proposed algorithm, the speed control of nonlinear DC motor are performed. Front the simulation results, we have found that the proposed algorithm is more superior to the conventional constant fain PID controller.

• Proceedings of the KAIS Fall Conference
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• 2003.11a
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• pp.236-242
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• 2003

ATM ABR service controls network traffic using feedback information on the network congestion situation in order to guarantee the demanded service qualities and the available cell rates. In this paper we apply the control method using queue length prediction to the formation of feedback information for more efficient ABR traffic control. If backward node receive the longer delayed feedback information on the impending congestion, the switch can be already congested from the uncontrolled arriving traffic and the fluctuation of queue length can be inefficiently high in the continuing time intervals. The feedback control method proposed in this paper predicts the queue length in the switch using the slope of queue length prediction function and queue length changes in time-series. The predicted congestion information is backward to the node. NLMS and neural network are used as the predictive control functions, and they are compared from performance on the queue length prediction. Simulation results show the efficiency of the proposed method compared to the feedback control method without the prediction. Therefore, we conclude that the efficient congestion and stability of the queue length controls are possible using the prediction scheme that can resolve the problems caused from the longer delays of the feedback information.

• Journal of KSNVE
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• v.6 no.5
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• pp.595-605
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• 1996

If the control force designed on the basis of the mathematical model with parameter errors is applied to control the actual system, the closed-loop performance of the actual system will be degraded depending on the degree of the errors, In this study, the effect of parameter errors on the robustness of several natural controls has been analyzed and compared. Every asymptoic stability condition for the natural controls has been derived using Lyapunov approach, and the characteristics of the stability conditions has also been compared. The extent of deviation of the closed-loop performance from the designed one for the natural controls is derived using operator techniques, and evaluated by numerical method. It has been found that the optimal control, acceleration feedback control, and acceleration-position feedback control among the considered natural controls would be robust one with respect to the parameter errors.

• Bulletin of the Korean Mathematical Society
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• v.25 no.2
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• pp.185-194
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• 1988

In [2], we have shown that the optimal boundary controls for hyperbolic systems in L$^{2}$-spaces can be attained in a feedback form via Riccati operators. A number of authors [1, 5, 7 and 10] have investigated approximations of Riccati operators arising in distributed parameter systems. They assumed bounded controls for parabolic systems. However, we in this paper study Galerkin approximations of Riccati operators and feedback controls for hyperbolic systems with unbounded control actions. Let us briefly introduce some results of [2]. Let .ohm. be an open bounded region in R$^{n}$ with smooth boundary .GAMMA. where n is a fixed positive integer. We consider a strictly hyperbolic differential operator H(x) of order 1 on .ohm. with noncharacteristic boundary on .GAMMA.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1896-1900
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• 2003

In this paper, a new type of output feedback control, called a receding horizon finite memory control (RHFMC), is proposed for stochastic discrete-time state space systems. Constraints such as linearity and finite memory structure with respect to an input and an output, and unbiasedness from the optimal state feedback control are required in advance. The proposed RHFMC is chosen to minimize an optimal criterion with these constraints. The RHFMC is obtained in an explicit closed form using the output and input information on the recent time interval. It is shown that the RHFMC consists of a receding horizon control and an FIR filter. The stability of the RHFMC is investigated for stochastic systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.7
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• pp.1346-1367
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• 2011

As the size of camera modules is decreasing and as the computing performance of portable devices is improving, taking photos has become a part of daily life. However, existing photo management programs and products that manage such photos still require extensive user effort to facilitate the sharing and browsing of images. It is especially difficult for novice users to manage and share photos. In this paper, we develop a round-robin concept-driven user preference feedback mechanism for achieving direct photo sharing, instant display, and easy management using optimized user controls and user preference-driven classification. Compared with commercial photo management systems, our proposed solution provides new features: optimized user controls, direct sharing and instant display, and user preference feedback driven classification. These new features boost the round-robin concept-driven user preference feedback. This paper proposes a photo finder that automatically searches for photos in storage spaces or cameras. The proposed photo finder relies on user preference feedback to share photos by leveraging user preferences, and the round-robin connection transmits photos to the family's digital photo frame or web album by arbiter. The proposed method saves time and spares users the effort required for photo management. Moreover, this method does not merely direct photo sharing and simple photo management, but it also increases the satisfaction level of users viewing the photos.

• International Journal of Safety
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• v.10 no.2
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• pp.10-15
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• 2011

The reconfigurable control systems based on feedback controls are utilized to compensate for damages of actuators in control systems. Such systems have multiple feedback controls and switch them in accordance with the degrees of the failures of the actuators. In order to be able to assess those systems, this paper develops a method to obtain reliabilities of reconfigurable dynamical systems which are interconnected in parallel / series configuration. By calculating reliabilities of interconnected dynamical systems, it is possible to assess many dynamical systems by comparing their reliabilities. Firstly, reliabilities of subsystems are obtained according to the definitions of the failures in terms of robust reliability for each subsystem. Then, the reliability of overall system is calculated from reliabilities of subsystems, using the methodology employed for probabilistic safety assessment. Failure rates of subsystems with feedbacks for reconfiguration change in certain time periods because of the switching of feedback controls. In order to deal with this, combinations of subsystems which compose overall system for each time period are derived by the methodology mentioned above and then integrated to calculate the reliability of overall system for a specific time. An illustrative example shows the validity and details of the proposed method.